All subjects will be admitted to the General Clinical Research Center (GCRC) of the South Texas Veterans Healthcare System, Audie Murphy Division, San Antonio, Texas on the day of the study between 6:45 and 8 AM. Subjects will not be allowed to eat or drink anything after 10 PM the night before, until the study is completed. At about 7:30 AM subjects will ingest 75 grams of glucose. Plasma samples for glucose, insulin and C-peptide concentrations will be drawn at -30, -15, and 0 minutes and every 15 minutes thereafter for two hours. At 30 minutes before the start of the OGTT, a muscle biopsy of the vastus lateralis muscle will be performed. After injection of xylocaine, a 5 mm incision is made 10-15 cm above the patella, and the biopsy needle is inserted into the muscle. The needle is connected to suction, and approximately 200 mg of muscle tissue is obtained. All muscle biopsies will be stored in liquid nitrogen within 15 seconds, until processing for specific assays.